This quantity for photons is equal to the power flux density over the speed of light. For an ideal gas, the specific heat at constant volume is equal to R less than the specific heat holding this quantity constant. Also for an ideal gas, this quantity, all else equal, is proportional to temperature and inversely proportional to volume. For 10 points, name this quantity defined as the ratio of the 
This quantity for photons is equal to the power flux density over the speed of light. For an ideal gas, the specific heat at constant volume is equal to R less than the specific heat holding this quantity constant. Also for an ideal gas, this quantity, all else equal, is proportional to temperature and inversely proportional to volume. For 10 points, name this quantity defined as the ratio of the magnitude of a force over the area over which it is exerted, often measured in torr or atmospheres.
This quantity for photons is equal to the power flux density over the speed of light.
{pressure}